Researchers from Carnegie Melon University and Karlsruhe Institute of Technology have recently published an article in Journal of the Royal Society titled Staying Sticky: Contact Self-Cleaning of Gecko-Inspired Adhesives that presents the first gecko-inspired adhesive that matches both the attachment and self-cleaning properties of gecko’s foot on a smooth surface.

Using glass microspheres to simulate contamination the scientists created a synthetic gecko adhesive that could self-clean and recover lost adhesion. Real world applications of self-cleaning adhesives are reusable adhesive tapes, clothing, medical adhesives (bandages) and pick-and-place robots, among others.

Everyday challenge with traditional adhesives is that they loose their stickiness once contaminated. Geckos have been intriguing researchers for decades because of their unique and striking capability to maintain the stickiness of their toes through contact self-cleaning. They can travel up the walls and ceilings in a wide variety of “dirty” settings retaining adhesion.

Upon experimentation, scientists discovered that the critical variable is the relative size of microfibers that make up the adhesive compared to the diameter of contaminant particles. Glass microspheres were used in diameters from 3 to 215microns. Glass microspheres were packed in air and used as supplied. Contamination of the samples was achieved by brining each sample in contact with a monolayer of glass microspheres with specific speeds under predetermined compressive loads. The cleaning process involved a load-drag-unload procedure.

Best self-cleaning results were obtained with the largest contaminants (glass microspheres), with the size of the adhesive fiber much smaller than the contaminating particle. This information is important to know when designing self-cleaning adhesives—make the adhesive fibers much smaller for improved adhesion recovery. This cleaning mechanism requires unloading particles by dragging. The other extreme of contaminating microspheres being much smaller than the adhesive fibers has advantages in some situations, even though it works by a different mechanism. Smaller microspheres tended to become embedded into the adhesive material. Particle embedding is a temporary cleaning process but might be sufficient in some applications.

Silica Nanospheres as Photonic Nanostructure Found in the ‘Disco’ Clam Ctennoides Ales

Scientists from UC Berkeley have recently discovered that a strange naturally occurring bright display of the ‘disco’ or ‘electric’ clam Ctenoides ales is actually a photonic display created by a layer of silica nanospheres. The display functions solely by reflecting light.

An article was published in the Journal of The Royal Society titled “A Dynamic Broadband Reflector Built from Microscopic Silica Spheres in the ‘Disco’ Clam Ctenoides Ales“, where the researchers shared their findings.

Laboratory elemental analysis of the reflective nanospheres showed that they are indeed composed of amorphous silica. Both the outer shells and the cores are composed of silica. Silica nanospheres are secreted by the animal and used as a light scattering structure in a behavior modulated reflective photonic display.

The measurements show that the diameter of the silica nanospheres is at around 300nanometers, an optimal particle size for scattering visible light, especially the shorter blue-green wavelengths of 400-500nm that predominate at 3-50m underwater, which is typically the clam’s habitat. In addition to the diameter, the highly organized packing structure of the nanospheres aid in the scattering of the visible light at the shorter wavelengths.

The display is so bright that it has been mistakenly thought of as bioluminescent, but the findings show that it is actually based on light scattered by photonic nanostructures.

Silica has a high index of refraction at n=1.43 at 589nm.

Silica Nanospheres - 300nm in diameter - available from CosphericNano

This study is extremely interesting to scientists in many different fields because it opens their minds up to many creative uses of silica nanospheres that have not been known before. The findings show a practical way to manipulate light in low light situations. Among its other advantages, silica, similar to glass, is a very durable material, with high melt point. Using silica nanospheres in tightly packed arrays to create photonic nanostructures seems like a great idea.

Highly precise and spherical silica nanospheres with narrow size distribution, diameters around 300nm and sphericity of greater than 99% in dry powder from can be purchased from CosphericNano—a new website specializing in precise silica nanospheres.

Black Paramagnetic Spheres and Micropsheres 10micron to 1.4mm

Black polyethylene paramagnetic microspheres are now available in wide selection of particle sizes ranging from 10 micron to 1.4 millimeters. The particles are supplied in dry powder form. No solvents are used in the manufacturing process. Black paramagnetic polymer microspheres have a strong response to magnetic fields and can be manipulated with a magnet. Highly opaque particles with maximum hiding power.

Paramagnetic microspheres have the ability to increase in magnetization with an applied magnetic field and loose their magnetism when the field is removed. Neither hysteresis nor residual magnetization is observed and that provides the end use two very practical advantages:

When the filed is removed, the microspheres demagnetize and re-disperse easily. This property allows efficient washing steps, low background and good reproducibility.

The behavior of the microspheres is always the same whatever the magnetization cycles may be. Such behavior is a key point for automated instrument.

According to Wikipedia, paramagnetic materials have a small, positive susceptibility to magnetic fields. These materials are slightly attracted by a magnetic field and the material does not retain the magnetic properties when the external field is removed. Paramagnetic properties are due to the presence of some unpaired electrons, and from the realignment of the electron paths caused by the external magnetic field.

Encyclopedia Britanica defines paramagnetism as a kind of magnetism characteristic of materials weakly attracted by a strong magnet, named and extensively investigated by the British scientist Michael Faraday beginning in 1845. Most elements and some compounds are paramagnetic. Strong paramagnetism (not to be confused with the ferromagnetism of the elements iron, cobalt, nickel, and other alloys) is exhibited by compounds containing iron, palladium, platinum, and the rare-earth elements.

Paramagnetic microparticles are used in numerous applications where they can be manipulated with a magnet, observed and cleaned-up for reuse.

Cospheric offers unique capability to manufacture Janus microspheres and microparticles with partial coatings and dual functionality. Currently half-shell or hemispherical coatings can be applied to any sphere (glass, polymer, ceramic) in sizes 45micron in diameter and higher. Coatings can be customized for any color and coverage of between 20% to 60% of the sphere. Each coating is custom formulated for color, charge, magnetic, electric, and surface properties, and solvent resistance per customers’ needs.

Hemispherical coatings of less than 1 micron with tolerances as low as 0.25 micron have been routinely demonstrated. Color combinations are truly unlimited. White, black, silver, blue, green, red, yellow, brown, purple as well as transparent microspheres have been made. Sphericity of greater than 90% and custom particle size ranges are offered.

Optically anisotropic spheres and janus particles with magnetic half-shells have been originally developed for applications in electronic displays, such as e-paper, but are now widely used in numerous applications in diagnostics, medical research, microscopy and biotechnology, as well as electronics, due to their ability to orient themselves in response to electromagnetic field and show a visual response. This is achieved by making spheres both bipolar and bichromal, with dipole precisely aligned with two differently colored hemispheres. As the spheres align themselves, the viewer will observe the color of one hemisphere, while the other hemisphere will be hidden from view, providing an obvious strong visible indication of the presence of the field or other stimuli. In alternating electromagnetic field, these microspheres have been proven to spin at hundreds of times per second.

In summer of 2013 BCC Research has issued an updated market research report on Microspheres: Technologies and Global Markets. According to the report, the global market for microspheres was estimated to total nearly $2.2 billion in 2012 and is projected to increase to $2.4 billion in 2013; the market should total $4.4 billion by 2018 and have a five-year compound annual growth rate (CAGR) for of 12.6%.

Analyses of global market trends, with data from 2012, estimates for 2013, and projections of compound annual growth rates (CAGRs) through 2018.

Identification of a variety of types of microspheres available on the market, as well as relevant industries, technologies and applications.

Examination of demand for microspheres in six major industries: composites, paints and coatings, oil and gas, cosmetics and personal care, biotechnology and life sciences, and medicine and medical devices.

Descriptions of different types of microspheres with respect to their chemical composition, including glass, ceramic, and polymer microspheres, and unique material properties that make them suitable for specific industries and applications.

BCC analyzes the global market for microspheres from both the manufacturing and demand points of view. Since there are several types of microspheres that vary drastically in quality, chemical properties, functionality and price, each type of microsphere is discussed in detail, including materials, manufacturing processes, advantages, prices and primary applications. Similarly, due to these variations microsphere use in six major industries are discussed and analyzed in detail.

Detailed analysis and market forecasts are provided per industry, type of microsphere and geographic region through 2018. The report describes major players in the industry and examines recent advances in technology, newly evolving markets and companies as well other factors influencing supply and demand.

This report analyzes microspheres—homogeneous microparticles of 1 micron to 1,000 microns in diameter. Microspheres can be solid or hollow and made from a variety of raw materials.

ANALYST CREDENTIALS

BEWARE of rip-off reports that have been published this year by Research and Markets, Transparency Market Research, and other non-USA-based research firms, they contain partially plagiarized (reworded) and some completely inaccurate information.

Yelena is the author of numerous applications, patents and published articles on microspheres technology and its applications and has held technical and managerial positions at Xerox Corp, Corning Inc., Cardinal Health, Gyricon, and Cbrite Inc. Yelena has a Bachelor’s degree in Chemical Engineering from Polytechnic University and a Master’s degree in Materials Science and Engineering from Rochester Institute of Technology, both in New York.